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In this talk, I will describe results on 1,220 electron pairs produced from a 207 Pb beam at 160A GeV in a nuclear experiment EMU 11 conducted at the CERN SPS. These electron pairs were produced at a distance of more than 50 μm from the primary interactions, which eliminates contamination due to Dalitz pairs. Results on electron pairs with invariant mass Q ranging between 1 and 100 MeV and life-time τ between 10−15 s and 10−12 s were analyzed. After subtracting background pairs from the materialization of photons and from the decays of π0 to photons from the data, they exhibit an enhancement at low mass Q = 6 – 20 MeV with narrow peaks at 7 ± 1 MeV , 19 ± 1 MeV and τ ≤ 10−13 s .

In the present paper charging and discharging transient currents in polyvinyl formal (PVF) were measured as a function of temperatures (40–80°C), poling fields (90 ×103−9.0 × 104 V/cm) and electrode combinations (Al-Al, Au-Al, Zn-Al, Bi-Al, Cu-Al and Ag-Al). The current-time characteristics have different values of slope lying between 0.42–0.56 and 1.42–1.63. The polarization is considered to be due to dipolar reorientation associated with structural motions and space charge relaxations due to trapping of injected charge carriers in energetically distributed traps.

An appreciable electric current is observed in a system consisting of a polyvinyl formal (PVF) film in a sandwich configuration, in the temperature range 30–110°C. The maximum value of the current during first heating is found to be of the order of 10−10 A and its thermograms exhibit one transition (i.e. current peak) at around 60°C. The position of the current peak in thermal spectrum shifts with the heating rate. A temperature dependence of the open circuit voltage is also observed. The activation energy of the process responsible for the current is determined. The magnitude of the current is more in the case of dissimilar electrode systems. It is proposed that the electric current arising from unpolarized metal-polymer-metal system is a water activated phenomenon, which is influenced by the transitional changes of the polymer.

The charge-transport behaviour in pure and chloranil (Chl) doped ethyl cellulose (EC) system has been studied by measuring the dependence of current on field, temperature, electrode material and dopant concentration. The role of doping molecular concentration in the polymer matrix and modification in the conduction characteristics are studied. Lowering of the activation energy due to doping was observed. The current was found to increase with an increase in the chloranil concentration. An explanation for this has been attempted on the basis of formation of molecular aggregates between chloranil molecules and ethoxy groups of ethyl cellulose. It is suggested that chloranil occupies interstitial positions between the polymer chains and assists in carrier transportation by reducing the hopping barriers. The current-voltage characteristics of different samples are analyzed using space charge limited current theory and quantitative information about the transport parameters is derived. The values of effective drift mobility and trapped charge carrier concentration which result in the build up of space charge have been calculated.

Transient discharging currents and steady-state conduction in solution-grown ethyl cellulose (EC)–poly(methyl methacrylate) (PMMA) blends measured as a function of temperature (30–80 °C) and field strength (10–100 kV cm−1) are reported. Transient currents are found to follow the Curie–VonSchweidler law, characterized by different slopes in short- and long-time regions, having different decay constant values lying between 0.75–0.99, and 1.68–1.95. The corresponding activation energies are found to increase with time of measurement of discharge current. Isochronal characteristics (ie current versus temperature plots at constant times) constructed from the data seem to reveal a broad peak observed at 60 °C. The dependence of dark current at different temperatures (30–80 °C) in a metal (1)–EC–PMMA blend–metal (1)/(2) system on the applied voltage in the range 10–100 kV cm−1 has also been studied; the current is found to be strongly temperature dependent. Dipole polarization and space charge resulting from trapping of injected charge carriers in energetically distributed traps and induced dipoles created because of the piling up of charge carriers at the phase boundary of the heterogeneous components of the blend are considered to account for the observed transient currents. The results of current–voltage measurement on blends are interpreted to show that the low-field steady-state conduction is ohmic in nature, and in high fields the charge carriers are generated by field-assisted lowering of coulombic barriers at the traps and are conducted through the bulk of the material by a hopping process between the localized states by a Jonscher–Ansari Poole–Frenkel mechanism. The modified P–F barrier is calculated to be 1.89 × 10−19 J (1.18 eV), 1.92 × 10−19 J (1.20 eV) and 1.95 × 10−19 J (1.22 eV) for P1, P2 and P3 blends, respectively. © 2000 Society of Chemical Industry

Thermally stimulated depolarization current (TSDC) studies have been performed on solution grown cellulose acetate films doped with different concentrations of acrylic acid (AA) prepared at the poling temperatures (40–75°C) with poling fields (10–50 kV/cm). The TSDC spectra of pure and AA doped CA films reveal two relaxation peaks at 80°C and 180 ±2°C, having activation energies centred around 0.25 and 0.55 eV. The phenomena of the existence of these current maxima have been analyzed and discussed in terms of the molecular motion of the polar side groups and release of the remaining part of the frozen dipoles by their cooperative motion with adjoining segments of the main polymer chain. The peak currents, released charge and activation energies associated with the peaks are affected by AA doping. The effect of doping with acrylic acid on the discharge current indicates the formation of molecular aggregates

Current-voltage (I–V) characteristics of pure polyvinyl formal (PVF) were investigated at different fields, range 5–100 kV/cm, as a function of temperature, range 313–363 K. It was observed that while at low fields (up to 25 kV/cm), the conduction was Ohm’s law-dependent at high fields (beyond 25 kV/cm), the conduction was Poole-Frenkel (P-F) mechanism-dependent. An attempt was made to identify the nature of the current by comparing its observed dependence on temperature, electric field and electrode materials with their respective characteristic features of the existing theories of electrical conduction. The current showed a strong dependence on temperature. To identify the possible mechanism of conduction, current versus square root of field characteristics were drawn with aluminium, silver, copper and gold as upper electrodes and Al as the lower electrodes. The observed characteristic suggested that the charge carriers were generated by the field-assisted lowering of coulombic barriers at the traps, and were subsequently conducted through the bulk of the material by a hopping process between the localized states by a Jonscher-Ansari-modified P-F mechanism. The calculated value of the modified P-F barrier was ⋍ 1·94×10−19 J (1·21 eV).

From the secondary interactions of projectile fragments (PFs) of charges Z > 30 from a beam at 10.6 A GeV from Brookhaven National Laboratory, in emulsion, we observed an increase of more than 51% in secondary interactions within a distance of from their production point. The loss of charge in interactions observed with PFs of charge is small. The short-range observations support the recent theoretical predictions of multihyper nuclei production which exhibit an enhanced interaction radius and these studies may lead to the detection of exotic particles.

The azimuthal angle correlations in pairs of projectile fragments (PFs) of charge Z = 2 and Z > 2 are studied in the Pb-emulsion interactions at GeV, as a function of their transverse momentum . The correlation strength increases with the centrality of the collision (except at b = 0), and is much larger than the Au data at GeV.

The charge (Z) distribution of multifragment decays of 197 Au projectile at 10.6A GeV in nuclear emulsion is fitted with a power-law. The moments of nuclear charged fragment distribution provide strong evidence that nuclear matter possesses critical point observables. The observed values of the critical exponents γ, β and τ are very close to those for a liquid–gas system.

By using the transverse momentum technique, we investigated the nuclear collective flow from the projectile fragments of charge Z ≥ 2 produced in the interactions of a 208 Pb beam at 160A GeV in nuclear emulsion. Flow is observed in a 208 Pb beam at 160A GeV and these results are compared with a 197 Au beam at 10.6A GeV.

We present the results of a study performed on the $^{208}\mathrm{emulsion}$ interactions at 160A GeV. In a minimum-bias sample of 1034 nuclear collisions, charges are assigned to all of the emitted 3431 helium and 1820 heavier projectile fragments during the breakup of the $^{208}\mathrm{Pb}$ beam in emulsion. Multiplicity distributions of the target-associated slow-moving particles and of the fast-moving projectile fragments are investigated. The polar angles of a subsample of 337 interactions having at least four projectile fragments of charge Z\ensuremath{\ge}2 are accurately measured and their pseudorapidity distributions are obtained. Multiplicity distributions, two- and three-body asymmetries, and conditional moments of the fast-moving projectile particles are investigated in terms of the total charge remaining in bound in the multiply charged projectile fragments. The results are compared with our existing 10.6A GeV $^{197}\mathrm{emulsion}$ data obtained in experiment No. 875 conducted at the Brookhaven National Laboratory. Multiplicity distributions of slow particles emitted from the $^{208}\mathrm{\ensuremath{-}}$ and $^{197}\mathrm{induced}$ emulsion reactions are found to be independent of the beam masses and their energies. An insignificant number of fission events is observed in this work. Some differences in the average yields of helium nuclei and heavier fragments are observed, which may be attributed to an energy effect or to the limited statistics. However, two- and three-body asymmetries and conditional moments indicate that the breakup mechanism of the projectiles over a wide span of energies seems to be energy independent. \textcopyright{} 1996 The American Physical Society.

The method of scaled factorial moments is used to study the fluctuations in the nuclear fragmentations of 197 Au at 10.6 A ·GeV by disentangling the peripheral from more central events. Intermittent behavior is found only in the midcentral processes. Clustering size distributions also exhibit power-law behavior. These observations indicate that the nuclear system might have gone through a phase transition.

We present an analysis on two- and three-particle correlations among shower particles, produced in semi-central collisions of197Au at 10.6A GeV with nuclear emulsion. Results are compared with the existing data of28Si ion at 14.5A GeV from BNL, and32S,16O nuclei at 200A GeV and16O beam at 60A GeV from CERN. Existence of short-range correlations is observed to be a general feature of all the heavy-ion reactions in pseudorapidity and azimuthal angle phase-spaces.

In ${}^{197}$Au-emulsion interactions at $10.6A\mathrm{GeV}$ from the Alternating Gradient Synchrotron at Brookhaven National Laboratory, the projectile fragments (PFs) of charge $Z\ensuremath{\ge}2$ exhibit collective flow which is observed in all interactions with different impact parameters. Collective flow increases with the charge of the PFs. But in the case of ${}^{28}$Si-emulsion interactions at $14.5A\mathrm{GeV}$, the PFs of ${}^{28}$Si do not show collective flow.

The charge distribution of multifragment decays of $^{197}\mathrm{Au}$ projectiles at 10.6A GeV in nuclear emulsion is fitted with a power law. The correlations between the charges emitted are given as a function of the total charge confined in fragments ${\mathit{Z}}_{\mathrm{bound}}$ for Z\ensuremath{\ge}2, which is a measure of the violence of the collision. The observables of the present experiment are compared to the $^{197}\mathrm{Au}$ beam at 600A MeV in the domain of limiting fragmentation and they are also reproduced by the predictions of the statistical and the percolation models. Small changes in the values of some of these observables are revealed in the two energies.

We present a systematic analysis on the helium projectile fragments produced from 10.6 A GeV197Auemulsion interactions in an experiment conducted at the Brookhaven AGS. Total charge changing and partial production cross-sections are measured experimentally on the basis of helium multiplicity. The multiplicity distribution of helium fragments which are produced collectively obey a KNO scaling. The transverse momentum distribution of these particles indicates that they are produced from two different independent sources.

The azimuthal angle distributions of charged pions with respect to the reaction plane determined by projectile heavy fragments is presented for 32S at 200A GeV. The squeezeout of pions perpendicular to the reaction plane for 28Si at 14.5A GeV and 197Au at 10.6A GeV is observed as a function of impact parameter (b) and the target mass.

Horizontal technique of multifractals has been employed to investigate the dynamical properties of the produced projectile fragments of charge Z ⩾ 2 in the interactions of 84Kr ions at 1.52 A GeV, 238U ions at 0.96 A GeV, and 56Fe ions at 2.1 A GeV in nuclear emulsion. The dynamical fluctuations in multiplicity distributions of projectile fragments are characterized by continuous multifractal spectra.

The techniques of scaled factorial moments and multifractals have been employed to study the dynamical fluctuations of the produced singly charged particles in collisions of84Kr ions at 1.52 A GeV in nuclear emulsion. The power law behaviors are observed in the data. The generalized dimensions are determined by using the methods of intermittency and multifractals.

Modified methods for computing multifractal moments [ital G][sub [ital q]] and scaled factorial moments [ital F][sub [ital q]] in terms of a new scaled variable [ital X] suggested by Bialas and Gazdzicki, have been employed to study the self-similar behavior of particle production in interactions [sup 28]Si at 14.5[ital A] GeV, [sup 16]O at 60[ital A] and 200[ital A] GeV, and [sup 32]S at 200[ital A] GeV with nuclear emulsion. Power-law dependences of the moments on the number of bins [ital M] of the new variable ([ital X]) have been observed in the data.

Formation of clusters in high-energy p-nucleus interactions at 800 GeV and 4He-nucleus interactions at approximately 11-140 A GeV has been investigated with the technique of pseudorapidity gap distributions. The existence of many-particle short-range correlations is observed in all cases. The estimated cluster sizes are larger in 4He-nucleus data than in p-nucleus data.

Multiplicity distributions of shower particles produced in high-energy heavy-ion collisions of28Si at 14.5A GeV,32S at 200A GeV,16O at 200A GeV and16O at 60A GeV have been studied in small pseudorapidity intervals of the forward and backward hemispheres in the perspective of negative binomial distributions. Different multiplicity parameters have also been computed for the two hemispheres separately, and their variations with phase-space interval size have been studied.

Multiplicity distributions of shower particles produced in high-energy collisions of proton at 800 GeV,4He at ≈ 11A GeV and ≈ 140A GeV, and28Si at 14.5A GeV have been analysed separately in forward and backward hemispheres. The data are well described by the negative binomial distributions (NBDs). The heavy-ion data of28Si agree well with the predictions for NBD of multistring Monte Carlo code VENUS. Similar analysis has been performed in different azimuthal angle intervals for the first time, for the nucleus-nucleus interactions, and the data here also are satisfactorily parametrised in terms of NBD.

We present the results on cumulant moments obtained from horizontally and vertically averaged factorial moments for the shower particles, produced in32S-emulsion at 200 A GeV,16O-emulsion at 200 A GeV,16O-emulsion at 60 A GeV,28Si-emulsion at 14.5 A GeV and proton-emulsion at 800 GeV. Except the cumulants of order two, all other moments are consistent with zero within their statistical uncertainties. The strength of correlation length for each beam is higher than the previously observed values.

The charge distribution of projectile fragments emerging from events of 84Kr at 1.52A GeV in nuclear emulsion is fitted with a power law. The method of scaled factorial moments is employed to study fluctuations in the nuclear fragmentations. An intermittent behavior is observed in the data and this may be due to the mixing of events produced under different excitation energies.

Pseudorapidity-interval dependence of multiplicity distributions of shower particles produced in high energy interactions of protons at 800 GeV, 4 He at ≈ 11 A GeV, and 28 Si at 14.5 A GeV in nuclear emulsions have been investigated. The multiplicity distributions and correlated moments are parametrised successfully in terms of a negative binomial distribution (NBD). The heavy-ion data for NBD agree well with the predictions of the multistring Monte Carlo code VENUS.

From the peripheral collisions of28Si projectile at 14.5 A GeV in nuclear emulsion, emerged4He nuclei among the projectile fragments, are followed for their interactions. Multiplicity and pseudorapidity distributions of the produced particles emanating from 366 inelastic4He induced emulsion reactions are compared with those of28Si at 14.5A GeV,4He at 140A GeV and proton at 800 GeV beams. Standard deviation of the Gaussian fittings to the pseudorapidity distributions for different values of average shower particle multiplicities represents an approximate measure of the impact parameter. Second moments of the multiplicity distributions of the shower tracks can be parameterized in terms of a universal polynomial dependence. Results agree quite well with the predictions of the multistring model VENUS.

In $^{84}\mathrm{Kr}$ interactions with nuclear emulsion at 1.52A GeV, nuclei with charge Z up to 36 have been measured as a function of the associated proton multiplicity. The data reveal the presence of a strong correlation between different types of collisions and proton multiplicities. In the study of multifragment decays, the average number of intermediate-mass fragments (3\ensuremath{\le}Z\ensuremath{\le}15) increases with the proton multiplicity, reaches a maximum 〈${\mathit{N}}_{\mathrm{IMF}}$〉=2.03 for the most violent collisions, and then decreases.

Corrected scaled-factorial-moments are calculated for the multiplicity distributions of shower particles in different phase spaces. An intermittency power-law is observed in the central collisions of32S and16O at 200A GeV,16O at 60A GeV and28Si at 14.5A GeV in nuclear emulsion.

The charge distribution of nuclear fragments for events of 131 Xe at 1.22A GeV in nuclear emulsion is fitted with a power law. Method of scaled factorial moments is used to study fluctuations in the nuclear fragmentations. An intermittent behavior is found in the data but no convincing evidence of critical phenomenon is observed in nuclear fragmentation.

From the peripheral collisions of a 32 S beam at 200A GeV in nuclear emulsion, He tracks among the projectile fragments are identified and are followed for their interactions. The multiplicity distributions and their fluctuations in pseudorapidity intervals of the shower particles produced with ~500 He interactions in emulsions are compared with 32 S and 16 O beams at 200A GeV and 16 O at 60A GeV interactions. It is primarily the geometry of the nuclear collisions that determines the shape of different distributions.

The charge distribution of nuclear fragments for the nonfissile events of {sup 238}U at 0.96{ital A} GeV in nuclear emulsion is fitted with a power law. The method of scaled factorial moments is used to study fluctuations in the nuclear fragmentations. An intermittent behavior is found in the data, but no clear evidence of critical phenomenon is observed in nuclear fragmentation.

We report the results on the electromagnetic dissociation of 14.5A GeV28Si and 200A GeV16O projectiles in nuclear emulsion. The overall charge changing production cross sections are determined experimentally and are found to agree reasonably well with those computed theoretically. The relative rate as a function of decay energy for various reaction channels are parameterized in terms of an exponential function. Majority of the events in the most prominent decay modes can be attributed to the excitation of giant dipole resonances. Multiplicity distributions of α particles emerged from nuclear as well as electromagnetic interactions are also investigated.

Scaled factorial moments are computed for the multiplicity distributions of the 28 Si -emulsion interactions at 14.5A GeV in one- and two-dimensional phase spaces. An intermittency power-law is observed for the central collisions. The observations are found to be different in higher dimensions and they are compared with the other heavy-ion projectiles.

Intranuclear cascading mechanism one of the important non-linear effects in high energy nucleusnucleus collisions is investigated. The data on multiplicity (ns) and pseudorapidity (η) distributions of shower particles produced by32S and16O at 200A GeV,16O at 60A GeV,28Si at 14.5A GeV and He at ≈140A GeV are presented and compared with the string model VENUS, which takes into account the cascade interactions of secondary particles. The effect of the intranuclear collisions on the distributions of versus is discussed for all the beams.

We report the measurements on partial production cross sections of the multiple helium fragments emitted in the interactions of {sup 28}Si ions at 14.5{ital A} GeV in nuclear emulsion. Interaction mean free paths of the helium fragments have been investigated on the basis of helium multiplicity and size of the target nucleus as a function of the distance from their production points. Multiplicity scaling in the produced helium fragments is also observed.

We report the multiplicity and angular distributions of the low energy target-associated particles from 32 S and 16 O induced reactions at 200 GeV/nucleon and 16 O induced reactions at 60 GeV/nucleon in emulsion. The results are compared with the Monte-Carlo Code VENUS.

The multifractal approach has been applied to particles produced in central collisions of 16 O ions at 60 and 200 GeV/n and 32 S ions at 200 GeV/n in nuclear emulsion. A new set of multiplicity moments G q is measured and from these moments the dimensional function D q is extracted which is found to decrease with the order q of the moment. From D q , the f ( α q ) spectra are determined for all the three projectiles, which are smooth functions characterizing the fluctuations of the experimental pseudorapidity distributions. These results are compared with the simulated events obtained from the Lund Monte Carlo code FRITIOF.

Electromagnetic dissociation of 200 GeV/nucleon $^{32}\mathrm{S}$ projectiles has been investigated in nuclear emulsion. It constitutes about 15% of the total number of events observed. The production cross section for the electromagnetic process has been found to increase with the projectile charge when compared with that of the $^{16}\mathrm{O}$ beam at the same energy per nucleon.

We report the analysis of multiplicity distributions of charged particles produced in central and minimum-bias interactions of 32S ions at 200 GeV/n and 16O ions at 200 and 60 GeV/n with nuclei of emulsion. The minimum-bias events exhibit scaling in normalized multiplicity distribution, while the central events do not. The pseudorapidity distributions in minimum-bias events show limiting fragmentation in the target region. We have also analysed the forward-backward multiplicity correlations using the concept of “mutual information”

The minimum bias events produced by interactions of 32S ions at 200 GeV/n and 16O ions at 200 and 60 GeV/n with emulsion target exhibit scaling not only in multiplicity distributions of the produced particles but also in their pseudorapidity distributions in the target (for all projectiles) as well as in the projectile rest frames (for 16O projectiles). Similar scalings are also seen in central events of 16O beams in their corresponding pseudorapidity distributions. The data agree well with the predictions of the Lund model FRITIOF.

Scaled factorial moments were calculated for multiplicity distributions in the pseudorapidity intervals of secondary particles produced by the interactions of 16O beams at 60 and 200 GeV/n, 32S at 200 GeV/n and protons at 800 GeV/c in nuclear emulsion. The extracted moments exhibit a power-law dependence on the pseudorapidity bin size, which is consistent with intermittent behavior. At a given incident energy, the intermittency strength decreases with the increase in multiplicity.

We present the analysis of multiplicity distributions of charged secondary particles produced in minimum bias and central interactions of $^{32}\mathrm{S}$ and $^{16}\mathrm{O}$ at 200A GeV, $^{16}\mathrm{O}$ at 60A GeV, $^{28}\mathrm{Si}$ at 14.5A GeV, and protons at 800 GeV with nuclear emulsion in terms of the information entropy and higher generalized fractal dimensions. Comparisons of the $^{28}\mathrm{Si}$ data with Monte Carlo model venus and $^{32}\mathrm{S}$ data with fritiof model are also presented.

We report the measurements on interaction mean free paths of the multiple He fragments produced by the collisions of $^{32}\mathrm{S}$ ions at 200 GeV/nucleon in nuclear emission. Within experimental errors, the mean free paths have been found to be independent of the He multiplicity and the size of the target nucleus.

The charge distribution of multifragments of the 208Pb beam at 160A GeV in nuclear emulsion has been fitted with a power-law. The moments of the resulting nuclear charged fragment distribution dis provide strong evidence that nuclear matter possesses critical point observables. The values of the critical exponents (γ, β and τ) extracted from the 208Pb beam are compared with the values for the 197Au beams at 10.6A GeV and 1A GeV. These values are very close to those for a liquid-gas system.

We have studied the azimuthal angle correlations in pairs of alpha particles, in Intermediate Mass Fragments (IMFs), and in higher order multiplets observed in 197 Au-emulsion interactions at 10.6 A GeV. The correlation functions for higher fragment multiplets (greater than three or more fragments) exhibit characteristic signatures which are enhanced compared to those of two-fragment correlation functions. The pure multiplet contribution is extracted from the observed higher-order correlation functions. The measurements of collective flow correlations in heavy-ion collisions are best obtained by studying several fragments with mixed charges including He fragments.

An analysis that does not require the determination of reaction plane on an event-by-event basis, and involves only azimuthal correlation function of the projectile fragment pairs, has been employed to measure the collective flow of nuclear matter. Using this technique, we study the flow of projectile fragments of charge Z\ensuremath{\ge}2 produced in $^{197}\mathrm{Au}$ induced-emulsion reactions at 10.6A GeV. The collective flow is observed to be the most pronounced in semicentral collisions. The results are compared with those of $^{28}\mathrm{Si}$ at 14.5A GeV, $^{238}\mathrm{U}$ at 0.96A GeV, $^{84}\mathrm{Kr}$ at 1.52A GeV, and $^{56}\mathrm{Fe}$ at 1.7A GeV.

The observed intermittent behavior in nuclear fragment distributions for [sup 238]U at 0.96[ital A] GeV, [sup 84]Kr at 1.52[ital A] GeV, and [sup 131]Xe at 1.22[ital A] GeV may be due to the mixing of fragments produced under different initial conditions. Intermittent effects are significantly reduced by selecting a sample under the same initial conditions. Except the cumulants of order two, all other moments are consistent with zero within their statistical errors.

Corrected scaled factorial moments are calculated for the multiplicity distributions in one- (pseudorapidity and azimuthal angle) and two-dimensional (the product of pseudorapidity and azimuthal angle) phase spaces. An intermittency power-law growth is observed in the central collisions of $^{32}\mathrm{S}$ and $^{16}\mathrm{O}$ at 200A GeV, $^{16}\mathrm{O}$ at 60A GeV, and He at \ensuremath{\approxeq}140A GeV, while for $^{28}\mathrm{Si}$ at 14.5A GeV it is observed for inclusive interactions in nuclear emulsion. The effect is much pronounced for higher dimensions. The data for the $^{16}\mathrm{O}$ beam at 200A GeV satisfy the condition for two phases occurring together.